This section provides background information related to the present disclosure which is not necessarily prior art.
In many climate control systems, a thermostat typically switches on a heating or cooling load by using a relay or other switching device to connect an “R” (hot) wire to the appropriate load terminal, e.g., a “W” terminal wired to a furnace/air handler or a “Y” terminal wired to a heat pump/air conditioner. Historically, bimetal strips or mercury switches were used in thermostats to make such connections. These switching devices were passive and did not need to be connected to electrical power in order to operate. Since thermostats that used such devices did not need power, installers typically did not wire a common (“C”) wire from the climate control system equipment to the thermostat.